Conventionally, grinding wheels are dressed by means of a tool in which a diamond is mounted in a holder and is presented to the wheel. These tools have notorious difficulties and pose problems both to the toolmaker and to the user. For one thing, diamonds contain hardness vectors (or grain) which must be identified by the toolmaker when he is mounting the diamond in its holder. For another thing, where the tool can be used in more than one orientation (by reason, for instance, of a cylindrical holder clamped in a complemental toolpost) the tool must be marked for correct orientation in the post.
Neglect by either toolmaker or user results in materially shorter life, and, as diamonds are expensive commodities, this is a serious consideration. There is the further aspect that, not only are diamonds expensive, but their availability is decreasing, and this is especially so in that, under current market conditions, maccle shapes, that is the flat trianguloid shape most suited for form dressing, are increasingly being diverted for use as gemstones.
Finally, the polished or shaped diamond must be so mounted as to be supported everywhere save at the exposed face which does the dressing, to bond the diamond mechanically to its support.
To avoid, or at least minimise, these disadvantages, it has been proposed to substitute the diamond stones by inserts of ultra hard material such a specialised compacts of diamond grit in a metal matrix, or ceramic materials. While the problems of orientation are avoided, the cutting element however is still fully supported. The tool is chisel shaped, with the central zone performing the dressing operation.
Traditionally the tool uses a diamond and the dressing operation has been a process which removes the unwanted material by crushing.
This process, which causes the projecting particle surfaces in the wheel to be crushed, has unhappy consequences. The friction generated between the tool and the wheel raises the temperature of the wheel and the tool undesirably. The increase in temperature causes the wheel diameter to expand, alters the datum position of the dresser and carbonizes the diamond. The crushing of the surface particles tends to leave too smooth a surface, creating fine dust which, in the interest of health, must be exhausted, and clogging of the wheel face. As some force has to be applied to the tool to cause the crushing action, holders, tool post, and tracing arms tend to be deflected, and thus must be correspondingly robust to resist deflection.
The object of the present invention is to provide a dressing method and a dressing tool which minimises still further the disadvantages of diamond tools, and which has substantial benefits over such tools.